1. Field Of The Invention
The invention relates to a method of and apparatus for monitoring waste influent streams to a secondary treatment biological basin containing active microorganisms to determine whether or not such influent streams contain levels of materials that are injurious to the microorganisms in the biological basin in ample time to take preventive measures to avoid substantial damage to the vitality of the active microorganisms in the basin. The method and apparatus of this invention directly compare the actual effect of a sample of the waste influent on the oxygen uptake of a sample of mixed liquor taken from the biological basin against the oxygen uptake of a control sample of mixed liquor taken from the biological basin and indicate the presence of materials toxic to the active microorganisms or the presence of highly degradable materials that can cause undue oxygen depletion and thus injury to the active microorganisms or a reject signal in the event of a malfunction or error.
2. Description Of The Prior Art
Biological waste treatment involves the oxidation of chemical compounds by active microorganisms to innocuous end products. Both the rate and the extent of oxidation are dependent upon the "health" of the microorganisms and the various properties of the influent waste. A common method for treating sewage to remove pollutants is by the activated sludge process. According to this process, the sewage, with or without primary clarification, is thoroughly mixed with oxygen-containing gas in the presence of aerobic bacteria in a basin of active microorganisms commonly called a secondary treatment basin. The organic matter contained in the sewage is absorbed and biologically oxidized by the bacteria. Subsequently, the bacteria are separated, e.g., by gravity settling, the purified effluent is decanted and discharged into a receiving stream or body of water with or without prior disinfection with chlorine or ozone.
The problems encountered in treating industrial wastes are more complex, especially in the secondary treatment, than with domestic wastes. Many synthetic industrial compounds produced by process units are inhibitory to the respiration of the biological microorganisms in the secondary waste treatment units. Therefore, a method of detecting potentially inhibitory conditions before the waste reaches the secondary unit is needed to protect the microorganisms in the secondary treatment units from large concentrations of highly toxic materials. Of equal importance, detection of highly degradable materials that can cause oxygen depletion in secondary biological basins is needed to prevent bulking and loss of the microorganisms in the final clarifier effluent. Control of these potential upsets is required to avoid severe damage to the secondary treatment basin, to avoid pollution of the stream or body of water receiving the effluent from the secondary treatment basin, and so that the treatment plant can conform to public waterway discharge permits. Inhibitory materials can either be low to high concentrations of potentially toxic compounds or high concentrations of readily degradable organic compounds. In the case of inhibitory toxic compounds, a percentage of the biological organisms are killed, thus reducing the efficiency of the secondary biological waste treatment or even rendering it ineffective. Readily degradable organics, on the other hand, can cause oxygen starvation and depletion in the biological basins, resulting in lowered efficiency and a loss of microorganisms from the final clarifiers because they will not settle out and are carried away with the effluent.
Previously, the secondary treatment unit was protected by detection systems inside the primary treatment boundaries. Many abnormal influent waste conditions were detected too late for correction or diversion. Commercially available oxygen uptake monitors are typically installed in the biobasin and measure the respiration of the biomass after influent waste water has been pumped into the aerobic biological basin. No positive corrective measures can be initiated at this point and it is usually too late to avoid damage and loss. Examples of prior art which measure the respiration of the biomass after the influent waste water has been pumped into the aerobic biological basin include U.S. Pat. Nos. 3,342,727; 3,348,409; 3,426,899; 3,510,407; 3,557,954; 3,731,522 and 3,740,320. U.S. Pat. No. 3,684,702 discloses a method and apparatus for determining the biochemical decomposability of sewage wherein various combinations of sewage and activated sludge are diluted with water and analyzed for BOD to determine the amount of activated sludge to be recycled to the aerating tank to provide optimum decomposition. This patent also describes a laboratory technique for determining toxic sewage waters wherein one analysis fermenter is continually supplied with sewage water, bacteria and additional nutrient while a second analysis fermenter contains only bacteria and the additional nutrient. If the oxygen consumption per time unit is smaller in the first fermenter than in the second, an impediment or poisoning of the bacteria is stated to exist. The different consumptions of oxygen can be utilized for releasing an alarm installation or for indicating countermeasures.
No prior art is known which discloses, teaches or suggests a method of or apparatus for measuring the actual effect of incoming sewage on mixed liquor obtained from the biological basin or lagoon of a secondary treatment unit before it enters the basin.